Conventional vehicle sound systems can include a plurality of dynamic or pistonic loudspeakers positioned at select locations throughout an interior or cabin of the vehicle. Such loudspeakers are known as “box speakers” because they typically comprise a rectangular- or square-shaped box enclosing one or more dynamic transducers (also known as “drivers”). Most box enclosures have an appreciable depth to accommodate the transducer(s) therein, which typically include a rigid basket or frame coupled to a cone diaphragm that is driven by a large magnet.
Given this depth, there are only a few locations within a typical vehicle interior that can accommodate box speakers. Some common speaker locations include the dashboard at the front of the vehicle interior, one or more doors on either side of the vehicle, or the parcel shelf located at the rear of the vehicle. In the case of low-frequency loudspeakers (e.g., woofer or sub-woofer), which are typically larger in size than middle or high frequency speakers (e.g., mid-range or tweeter), the speakers may be located in a trunk compartment of the vehicle, which can readily accommodate the larger speakers, albeit at the cost of cargo space within the trunk.
As an example, FIG. 1 illustrates a conventional loudspeaker arrangement that may be found in an existing vehicle 100 (e.g., a four-door sedan). As shown, the vehicle 100 includes a sound system comprising a plurality of conventional box speakers 102 positioned at various locations on front and back doors 104, 106 of the vehicle 100. As will be appreciated, the depicted doors 104, 106 constitute only one side of the vehicle 100, and an opposite side of the vehicle (not shown) may be a mirror image of the doors 104, 106 and may include additional box speakers 102 located in similar locations. As is conventional, the sound system of the vehicle 100 also includes a low-frequency loudspeaker 108, or woofer, located in a trunk 110 of the vehicle 100.
One drawback of conventional vehicle sound systems is the amount of wiring and manufacturing complexity required as a result of placing each of the loudspeakers 102 and the woofer 108 in discrete locations throughout the vehicle 100. For example, as shown, each of the loudspeakers 102 and the woofer 108 is electrically connected to an audio processor 114 of the vehicle sound system by a separate one of a plurality of cable harnesses 112. Further, each of the multiple cable harnesses 112 has a different length and/or follows a different path across the vehicle 100, thereby increasing the wiring complexity of the vehicle sound system.
Another drawback of the conventional vehicle sound systems is the reduction in cargo space caused by placing the speakers 102 within the doors 104, 106 and placing the woofer 108 in the trunk 110. As used herein, the terms “cargo area” or “cargo space” refers to user-accessible storage space within the passenger cabin and/or trunk of the vehicle and may include or form a pocket, compartment, cup holder, or other storage receptacle. As shown in FIG. 1, for example, each of the doors 104 and 106 includes a conventional cargo area 116, 118 within a lower half of the door below respective windows 120, 122. Like the woofer 108, which occupies valuable trunk space, the loudspeakers 102 integrated into the doors 104, 106 can reduce or limit the amount of available cargo area 116, 118 in each door. For example, as shown in FIG. 1, the cargo areas 116, 118 are carved out of the space that is not occupied by the box speaker 102. As will be appreciated, though not shown here, the space highlighted as cargo areas 116, 118 may also include one or more lights, handles for opening and/or closing the respective vehicle door, and buttons, knobs, levers, or the like for controlling the vehicle window(s), door lock(s), and/or side mirrors, as is conventional.
To further illustrate the available cargo area in a conventional vehicle door, FIG. 2 shows a cross-sectional side view of a lower portion of the back vehicle door 106. As will be appreciated, a cross-sectional view of the front vehicle door 104 may be substantially similar to the view shown in FIG. 2. In FIG. 2, the door 106 includes an interior door panel 124 coupled to an exterior side 126 of the door 106, and the door panel 124 comprises an internal storage compartment, or cargo area 118. The cargo area 118 is defined or formed by a cavity between an interior wall 128 of the door panel 124 that is coupled to the exterior side 126 of the door 106, and an exterior wall 130 that extends out from a base 132 of the panel 124 towards the passenger or cabin compartment of the vehicle 100. In accordance with the conventional speaker arrangement shown in FIG. 1, box speaker 102 is mounted to the interior wall 128 of the door panel 124, thereby reducing a size of the available cargo space 118 by at least a volume of the box speaker 102.
Existing solutions to the above-noted problems include placing flat or low profile speakers in a roof the vehicle. For example, U.S. Pat. No. 8,848,938 describes integrating electrostatic planar speakers into a roofliner of the vehicle, so that the roofliner itself is formed from the panel material of the planar loudspeaker. As another example, Japanese Patent No. 3808015 describes placing a distributed mode, flat panel loudspeaker just behind the headliner in a roof of a vehicle and using the headliner as the speaker cover. The Japanese patent also describes integrating the flat panel speakers into alternative locations, including the door trims, the pillar garnish, and the instrument panel. In another example, U.S. Pat. No. 6,377,695 describes placing distributed mode, panel speakers in the roof lining above the passenger compartment of a vehicle, where the acoustic radiator of each speaker is attached directly to an underside of the roof lining.
However, these existing solutions have several drawbacks, including a lack of bass or low-frequency response from both the electrostatic speakers and the distributed mode, flat panel speakers. As a result, such vehicle sound systems will typically still include a conventional sub-woofer, or other box loudspeaker for handling low-frequencies, that can only be accommodated in the trunk of the vehicle due to its sheer size and the above-noted space constraints in the passenger compartment. Accordingly, even though existing solutions may increase cargo space in the passenger cabin, a portion of the trunk space may still be occupied by the vehicle sound system.